1. Field of the Invention
An aspect of the present invention relates to a float valve apparatus suitable for use as a fuel fill-up control valve, a cut valve or a similar valve to be mounted on, for example, the fuel tank of a car.
2. Description of the Related Art
On the fuel tank of a car, there is mounted a fuel fill-up control valve which, when fuel is supplied up to the fill-up position of the fuel tank, closes the opening of the fuel tank communicating with the outside to stop the supply of the fuel.
Also, there is provided a cut valve which not only releases fuel steam to a canister but also, when the car jolts heavily while running or the car rolls over, closes an opening communicating with the canister to prevent the fuel from leaking to the outside.
As such fuel fill-up control valve and cut valve, there is employed a float valve apparatus structured such that it can be moved upward according to a rise in the liquid surface of the fuel to close the opening of the valve apparatus.
However, in such float valve apparatus, when the car runs along a rough road, the float valve can collide with the bottom surface of a housing to generate a strange sound.
JP-UM-H06-040552-A discloses a fuel leakage preventive valve structured such that a float valve disposed within a room formed in the housing can be moved up and down. Specifically, in the disclosed fuel leakage preventive valve, a separately-formed elastic buffer is interposed between the lower surface of the float valve and the receiving surface of the housing disposed opposed to the float valve lower surface. Since the lower surface of the float valve is elastically supported by the elastic buffer from the opposed receiving surface of the housing, even when the float valve is going to move up and down within the room due to the running vibration of the car or the like, the strong collision therebetween are buffered, and the generation of the loud strange sound is effectively reduced.
JP-H07-035255-A discloses a fuel cut valve including: a valve housing mounted on the upper surface portion of a fuel tank; a valve port formed within the valve housing and communicating with the ventilation line for fuel steam through a downstream side passage projecting outwardly of the housing; and a float valve for detecting the liquid surface level inside the fuel tank to open or close the valve port. In this fuel cut valve, a slit is formed in the bottom portion of the valve housing, whereby a cantilever valve body support portion is formed as an integral portion.
However, in JP-UM-H06-040552-A, since the elastic buffer for supporting the lower surface of the float valve is disposed outside a spring for urging the float valve upwardly, the outside diameter of the elastic buffer is large, which makes it difficult to set the load, free length and the like of the elastic buffer with high accuracy. Also, since, when the float valve is moved down in an inclined manner, the load concentrates on the local portion of the large outside diameter elastic buffer, there is raised a possibility that the collision of the float valve with the housing cannot be controlled sufficiently.
In JP-H07-035255-A, when the valve housing is formed of hard resin from the viewpoint of heat resistance, the elasticity of the cantilever valve body support portion is poor, which lowers the hitting sound reduction effect when the valve housing is collided with the float valve. Also, when the cantilever valve body support portion is formed thin in order to enhance the elasticity thereof, it is easy to break.